POS1142 A CONCORDANCE STUDY OF CT DENSITOMETRY WITH DXA DENSITOMETRY
Authors: R. Mawella, R. Rajak
Journal: Annals of the Rheumatic Diseases (2022)

Background Osteoporosis is a skeletal disorder characterised by compromised bone strength resulting in an increased risk of fracture. Although DXA is the only technology that can be used for diagnostic classification of osteoporosis according to WHO, computed tomography imaging (CT) densitometry of the spine has equal or superior ability to predict vertebral fractures in postmenopausal women. Therefore the continued use of DXA as the primary modality of calculating BMD may lead to inaccurate exclusion of osteoporosis and prognostication. Objectives To assess the concordance of spinal CT densitometry with current standard of assessment through DXA-derived densitometry. Methods 50 patients who had had both a DXA scan of the lumbar spine and CT lumbar spine/thorax/abdomen performed within 18 months of each other were included. The CT images were analysed to attain a mean Hounsfield score of the lumbar vertebrae and this was compared to DXA derived T-scores. A Hounsfield score of 131 was used as the threshold for diagnosing osteoporosis akin to a DXA-derived T score of -2.5. The final data was analysed to find correlation values of Hounsfield score with T-score using Pearson correlation coefficient. Results The mean Hounsfield score was 108.4 (osteoporotic) compared to a mean T-score of -1.22 (osteopenic) with a statistically significant correlation coefficient of 0.447, (p&lt;0.01). Using T score ≤ -2.5, 15 (30%) of the patients included on our study would have a diagnosis of osteoporosis whereas this would be 36 patients (72%) if using the threshold of Hounsfield score &lt;131. Out of the 50 patients included, 15 had vertebral fragility fractures. The mean T-score for these patients was -1.2 (indicating osteopenia) and mean Hounsfield score was 108 (indicating osteoporosis). Conclusion Our study showed a moderate positive correlation between the DXA-derived T-scores and CT Hounsfield scores. This further validates previous studies that suggest CT scans can be used to identify patients with osteoporosis. 93% of patients with vertebral fragility were identified as having osteoporosis using CT densitometry whereas only 40% were identified via DXA. These findings highlight the limitations of DXA, particularly in terms of overestimation of bone mineral density related to degenerative changes. CT images of the thorax, abdomen or lumbar spine that have already been performed for other indications can be used to opportunistically screen for osteoporosis without additional radiation exposure, waiting time or cost. This may allow for more accurate diagnosis and subsequent treatment and fracture risk reduction. References [1]Bartl, R. and Bartl, C., 2019. The Osteoporosis manual; Prevention, Diagnosis and Management . Germany: Springer International Publishing. [2]Engelke K, Adams JE, Armbrecht G, Augat P, Bogado CE, Bouxsein ML, et al. Clinical use of quantitative computed tomography and peripheral quantitative computed tomography in the management of osteoporosis in adults: the 2007 ISCD Official Positions. J Clin Densitom. 2008 Jan-Mar;11(1):123–62. [3]Bolotin HH. DXA in vivo BMD methodology: an erroneous and misleading research and clinical gauge of bone mineral status, bone fragility, and bone remodelling. Bone. 2007 Jul;41(1):138–54 Disclosure of Interests None declared